Which statement best describes what a quasar is?

Which statement best describes what a quasar is?

• A. An extremely luminous, distant object that appears star-like but emits strong radio energy
• B. A nearby variable star with unusual colors
• C. A type of planet orbiting a distant star
• D. A small comet near the Sun

Answer: (A)

Quasars are extremely luminous centers of distant galaxies powered by gas falling into a supermassive black hole. Because they are so far away, they appear like point-like, star-like sources, yet their energy output is staggering and detected across the electromagnetic spectrum, often with strong radio emission. This combination—star-like appearance due to distance, enormous intrinsic brightness from an active galactic nucleus, and significant radio emission—makes the description in the statement the best fit. The other options describe objects that don’t match these characteristics: a nearby variable star, a planet, or a comet.

Quasars are extremely luminous centers of distant galaxies powered by gas falling into a supermassive black hole. Because they are so far away, they appear like point-like, star-like sources, yet their energy output is staggering and detected across the electromagnetic spectrum, often with strong radio emission. This combination—star-like appearance due to distance, enormous intrinsic brightness from an active galactic nucleus, and significant radio emission—makes the description in the statement the best fit. The other options describe objects that don’t match these characteristics: a nearby variable star, a planet, or a comet.